Cardiovascular and nitric oxide response after maximal voluntary isometric contraction in adolescents with and without Down Syndrome

Este estudo teve como objetivo comparar as respostas cardiovasculares e de óxido nítrico (NO) à contração isométrica voluntária máxima (CIVM) com diferentes grupos musculares (leg press [LEP] e preensão manual isométrica [IHG]) de adolescentes com e sem síndrome de Down (SD). Alem de comparar a força IHG absoluta e relativa entre os grupos. Onze adolescentes com SD (14,1 ± 1,0 anos) e dez sem SD (13,7 ± 1,25 anos) realizaram duas sessões experimentais de exercícios LEP e IHG: 1) sessão de familiarização e 2) 3 tentativas x 5 segundos de contração na CIVM com 3- intervalo mínimo de descanso. A pressão arterial (PA), a frequência cardíaca (FC) e o NO foram coletados em repouso, imediatamente após a sessão de exercício e 10 minutos após o exercício. A dosagem de NO na saliva foi realizada pelo método colorimétrico de Griess. Não houve diferenças para respostas cardiovasculares e NO entre os grupos para CIVM. No entanto, o SD teve uma resposta cardiovascular menor, mas não significativamente, em repouso e após os testes de CIVM do que aqueles sem SD. O grupo SD apresentou maior concentração de NO em repouso, recuperação e após IHG quando comparado ao grupo não SD (P <0,05). Além disso, adolescentes com SD apresentaram menor nível de força de IHG absoluta e relativa quando comparados àqueles sem SD (P = 0,001). Indivíduos com SD apresentam menor resposta cardiovascular em repouso e após testes de CIVM e maior resposta de NO após o exercício quando comparados ao grupo sem SD.

The Association between Symmetrical or Asymmetrical High-Arched Feet and Muscle Fatigue in Young Women

The foot arches are responsible for proper foot loading, optimal force distribution, and transmission throughout the soft tissues. Since the foot arch is an elastic structure, able to adapt to forces transmitted by the foot, it was reported that low arch is related to excessive foot pronation, while high arched foot is more rigid and inflexible. Therefore, it is also probable, that foot arch alterations may change the force transmission via myofascial chains. The objective of this study was to evaluate the effect of symmetrical and asymmetrical excessive feet arching on muscle fatigue in the distal body parts such as the lower limbs, trunk, and head. Seventy-seven women (25.15 ± 5.97 years old, 62 ± 10 kg, 167 ± 4 cm) were assigned to three groups according to the foot arch index (Group 1—both feet with normal arch, Group 2—one foot with normal arch and the other high-arched, Group 3—both feet with high-arch). The bioelectrical activity of the right and left hamstrings muscles, erector spine, masseter, and temporalis muscle was recorded by sEMG during the isometric contraction lasting for 60 s. The stable intensity of the muscle isometric contraction was kept for all the time during the measurement. Mean frequency difference (%), slope (Hz), and intercept (Hz) values were calculated for muscle fatigue evaluation. No differences were observed in fatigue variables for all evaluated muscles between the right and left side in women with symmetrical foot arches, but in the group with asymmetric foot arches, the higher muscle fatigue on the normal-arched side compared to the high-arched side was noted. Significantly greater values of the semitendinosus—semimembranosus muscle frequency difference was observed on the normal-arched side compared to the high-arched side (p = 0.04; ES = 0.52; −29.5 ± 9.1% vs. −24.9 ± 8.4%). In the group with asymmetric foot arches, a significantly higher value of lumbar erector spinae muscle frequency slope (p = 0.01; ES = 1.32; −0.20 ± 0.04 Hz vs. −0.14 ± 0.05 Hz) and frequency difference (p = 0.04; ES = 0.92; −7.8 ± 3.1% vs. −4.8 ± 3.4%) were observed on the high-arched foot side compared to the side with normal foot arching. The thoracic erector spine muscle frequency slope was significantly larger in women with asymmetrical arches than in those with both feet high-arched (right side: p = 0.01; ES = 1.25; −0.20 ± 0.08 Hz vs. −0.10 ± 0.08 Hz); (left side: p = 0.005; ES = 1,17; −0.19 ± 0.04 Hz vs. −0.13 ± 0.06 Hz) and compared to those with normal feet arches (right side: p = 0.02; ES = 0.58; −0.20 ± 0.08 Hz vs. −0.15 ± 0.09 Hz); (left side: p = 0.005; ES = 0.87; −0.19 ± 0.04 Hz vs. −0.14 ± 0.07 Hz). In the group with asymmetric foot arches, the frequency difference was significantly higher compared to those with both feet high-arched (right side: p = 0.01; ES = 0.87; −15.4 ± 6.8% vs. 10.4 ± 4.3%); (left side: p = 0.01; ES = 0.96; 16.1 ± 6.5% vs. 11.1 ± 3.4%). In the group with asymmetric foot arches, a significantly higher value of the masseter muscle frequency difference was observed on the high-arched side compared to the normal-arched side (p = 0.01; ES = 0.95; 6.91 ± 4.1% vs. 3.62 ± 2.8%). A little increase in the longitudinal arch of the foot, even though such is often not considered as pathological, may cause visible changes in muscle function, demonstrated as elevated signs of muscles fatigue. This study suggests that the consequences of foot high-arching may be present in distal body parts. Any alterations of the foot arch should be considered as a potential foot defect, and due to preventing muscle overloading, some corrective exercises or/and corrective insoles for shoes should be used. It can potentially reduce both foot overload and distant structures overload, which may diminish musculoskeletal system pain and dysfunctions.

Alterations of tibialis anterior muscle activation pattern in subjects with type 2 diabetes and diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is associated with loss of motor units (MUs), which can cause changes in the activation pattern of muscle fibres. This study investigated the pattern of muscle activation using high-density surface electromyography (HD-sEMG) signals from subjects with type 2 diabetes mellitus (T2DM) and DPN. Thirty-five adults participated in the study: 12 healthy subjects (HV), 12 patients with T2DM without DPN (No-DPN) and 11 patients with T2DM with DPN (DPN). HD-sEMG signals were recorded in the tibialis anterior muscle during an isometric contraction of ankle dorsiflexion at 50% of the maximum voluntary isometric contraction (MVIC) during 30-s. The calculated HD-sEMG signals parameters were the normalised root mean square (RMS), normalised median frequency (MDF), coefficient of variation (CoV) and modified entropy (ME). The RMS increased significantly (p = 0.001) with time only for the DPN group, while the MDF decreased significantly (p < 0.01) with time for the three groups. Moreover, the ME was significantly lower (p = 0.005), and CoV was significantly higher (p = 0.003) for the DPN group than the HV group. Using HD-sEMG, we have demonstrated a reduction in the number of MU recruited by individuals with DPN. This study provides proof of concept for the clinical utility of this technique for identifying neuromuscular impairment caused by DPN.

Effect of percutaneous electrical stimulation of the spinal cord on the manifestation of reciprocal and presynaptic inhibition α-motor neurons of the lower leg muscles against the background of a weak isometric contraction in magnitude

The article presents the results of a study of the reflex mechanisms of reciprocal and presynaptic inhibition at rest and when performing an isometric reduction of 5% of MPS against the background of twenty-minute non-invasive electrical stimulation of the spinal cord. It was found that at rest against the background of electrical stimulation, reciprocal and presynaptic inhibition was inverted to their relief, and when performing plantar flexion of the foot, on the contrary, reciprocal and presynaptic inhibition increased, but the severity of presynaptic inhibition was greater. Key words: percutaneous electrical stimulation of the spinal cord, reciprocal inhibition, presynaptic inhibition, isometric contraction.

Comparison of post-activation performance enhancement (PAPE) after isometric and isotonic exercise on vertical jump performance

Purpose This study aimed to compare the post-activation performance enhancement (PAPE) induced by isometric and isotonic exercise on vertical jump performance. Methods 18 healthy trained men (25.8±2.7 years; 78.4±8.2 kg; 175.7±6.1 cm; 25.4±1.8 BMI; 126.72±10.8 kg squat 1-RM) volunteered for this study. They randomly performed two different PAPE protocols: Isotonic squats (ISOTS), which consisted of 2 sets of 3 repetitions at 75% of one-maximum repetition (1-RM); and isometric squats (ISOMS), which consisted of 2 sets of 4 seconds of submaximal (75% of 1-RM) isometric contraction at 90°-knee flexion. Countermovement jump (CMJ) height was tested at baseline and 4 minutes after each conditioning set. Results CMJ height significantly increased after set 1 in both PAPE protocols (ISOMS: p <0.001; ES = 0.34; ISOTS: p <0.001; ES = 0.24), with respect to the baseline jump. However, after set 2 no significant changes in CMJ height were observed for any protocol (ISOMS: p = 0.162; ES = 0.11; ISOTS: p = 0.976; ES = 0.06). No significant differences (p>0.05) were found between both isometric and isotonic exercise conditions. Conclusions Despite both protocols showed similar PAPE effects on CMJ height after set 1, none of the protocols demonstrated greater efficacy in increasing subsequent performance in healthy trained men.

Cardiovascular and nitric oxide response after maximal voluntary isometric contraction in adolescents with and without Down Syndrome v1

Background This study was designed to compare the cardiovascular and nitric oxide (NO) responses to maximal voluntary isometric contraction (MVIC) with different muscle groups (leg press [LEP] and isometric handgrip [IHG] exercise) of adolescents with Down syndrome (DS) and age-matched non-DS peers. We also aimed to compare the absolute and relative IHG strength between groups. MethodsEleven adolescents with DS (14.1 ± 1.0 years) and ten without DS (13.7 ± 1.25 years)participants performed two experimental sessions of LEP and IHG exercises: 1) familiarization session and 2) 3 attempts x 5-sec contraction at MVIC with 3-min rest interval. Blood pressure (BP), heart rate (HR) and NO were collected at rest, immediately post-exercise session, and 10-min post-exercise. Results There were no differences for cardiovascular and NO responses between groups for MVIC test using different muscle groups. However, DS group displayed a lower but not significantly cardiovascular response at rest and after MVIC tests than controls. Furthermore, DS group displayed a higher NO- concentration at rest, recovery and after IHG when compared to controls (P< 0.05). In addition, DS adolescents displayed a significantly lower level in absolute and relative IHG strength when compared to controls (P = 0.001). Conclusions Individuals with DS display a lower cardiovascular response at rest and after MVIC tests than controls and higher NO response after exercise.

Validity, Agreement and Accuracy of A Hand-Held Dynamometer for Shoulder Muscles Strength Assessment in Healthy Individuals

Background: The shoulder complex has a high prevalence of injuries. It is fundamental to quantify the muscle strength and identify muscular imbalances that predispose to lesions. The aim was to test concurrent validation of the muscle strength assessment with a hand held dynamometer (HHD) for shoulder joint muscles, and measure the accuracy and diagnostic agreement between instruments for assessing the strength of this joint with the hand held dynamometer and isokinetic dynamometer (ID) in a population of healthy individuals Methods: healthy individuals aged between 18 and 40 years were included. The HHD was used to test the isometric contraction of the main shoulder movements. Isometric contraction was performed for 3 seconds. Assessments with HHD and DI were performed on the same day, with a minimum interval of 90 minutes between tests. The study was approved by the Ethics Committee by report No.1537948. Concurrent validation was calculated with Pearson’s correlation, the accuracy obtained by the ROC curve and agreement by Kappa test. Results: The HHD showed concurrent validation between 0.51 – 0.83, with sensitivity between 0.90 and 0.98 and specificity between 0.64 and 0.89 for shoulder movements. The HHD demonstrated moderately-strong to excellent concurrent validity. Conclusion: These results are encouraging for the routine use of this portable and lower cost instrument in quantification of the pique torque of the shoulder muscles. Moreover, this instrument showed good accuracy and moderate to high agreement in comparison with diagnosis of the gold standard instrument.

Impact of Self-Selected Customized Orthotics on Lower Limbs Biomechanics

Customized insoles are commonly prescribed to prevent or treat a variety of foot pathologies and to reduce foot and lower limb fatigue. Due to the patient-specific design and production of such orthotics, the concept of self-selected customized orthotics (SSCO) has recently been developed. The goal of this study was to assess the impact of SSCO technology on several physiological and biomechanical variables during uphill power walking. Thirty male participants underwent an uphill power walking intervention at constant speed in two insoles conditions (control and SSCO). The electromyographic (EMG) activity of their right gastrocnemii and vastii muscles was measured. Perceived fatigue was assessed every 5 minutes and the intervention stopped when the targeted fatigue level was reached. Baseline and post-intervention assessments were also performed. Sixty-three percent of the participants experienced an improvement in foot fatigue while wearing the SSCO. The foot arch seemed to collapse less when participants wore the SSCO, but statistical significance was not reached. The changes in mean EMG activity was not consistent between the 50% isometric contraction and the walking trial. In conclusion, while some interesting trends were observed when wearing SSCO, further investigations should be performed to try and reach statistical significance.

Superior training efficacy of beginning movement load training for the baseball throwers

Background Superior shoulder motion with rotator cuff activation are essential for the performance of the throwing athletes. The present study compared the novel beginning movement load training (BMLT) and popular throwers ten program regarding the training efficacy of baseball throwers. We hypothesized that the BMLT contributed the superior training efficacy than popular throwers ten program. Methods Forty adult baseball players were randomized into study group and control group equally. In study group, the cyclic shoulder motion was repeatedly operated 3 days in a week and lasted for 6 weeks using three different BMLT training machines. As for control group, three popular cyclic training in the throwers ten program were adopted for the shoulder trainings as the same protocol in study group. The evaluations before and after training included the static range of motion (ROM), the maximal voluntary isometric contraction (MVICs) of the target muscle (pectoralis major, middle deltoid and supraspinatus) and throwing velocity. Result After 6-week course, study group had significant wider static ROM in saggital adduction (p = 0.002), coronal internal rotation (p = 0.018) and external rotation (p = 0.044) than in control group. The maximal voluntary isometric contraction (MVIC) ratio of middle deltoid/supraspinatus was significant lower in study group (Study:Control = 1.14 ± 0.76:3.56 ± 5.57, p = 0.049) which indicated the enhanced supraspinatus maximal contraction in the study group after training. In addition, the study group had significant improvement in throwing speed (117 ± 10 vs. 109 ± 10 km/h, p = 0.040). Conclusion The BMLT contributed the superiority in range of motion, recruitment of supraspinatus and throwing velocity than the popular thrower’s ten program. It could be a favourable training for the overhead activity.